Field experience has shown that water ice is a serious problem for couplings in repetitive transfers of cryogenic fluids. As the coupling warms on its storage rack after the transfer of a cryogenic fluid, it collects frost. The frost forms at any place that ambient air can reach. When the coupling reaches 32.degree. F., the frost melts and leaves water on all surfaces inside and outside of the coupling where the frost had formed. When the next transfer of the cryogenic fluid occurs before the coupling has had time to dry, the coupling is attached wet. The transfer of the cryogenic fluid then freezes the water to ice. The coupling is then difficult and sometimes impossible to uncouple and remove.
It is also important in the transfer of certain cryogenic fluids, such as liquid natural gas (LNG) to minimize the amount of cryogenic fluid that is most when the coupling is disconnected. A further important consideration for cryogenic couplings is that they couple and uncouple easily and do not leak cryogenic fluid while in service and under pressure. A further important consideration for cryogenic fluid couplings is that they must be a "quick" connection. The use of a wrench for making and breaking the coupling would not be acceptable.
Accordingly, it is a principal object of the present invention to provide a coupling for the transfer of cryogenic fluids that is quickly and easily connected, that is quickly and easily disconnected and that water ice cannot buildup to interfere with the operation of the coupling. It is also an objective of the present invention that any loss of cryogen during the coupling and uncoupling be kept to an absolute minimum. It is also an object of the present invention to provide safety locking mechanisms to prevent the flow of cryogen while the coupling is not connected to the receiving tank as well as to prevent the flow of cryogen while the coupling is being removed from the receiving tank. It is also an object of the present invention to provide protection for the operating person from cold and accidental spray of cryogenic fluid being transferred. It is also an object of the present invention to provide drop protection for the coupling and to provide warm means for the operating person to handle the coupling. It is also an object of the present invention to provide handle means for the operating persons used in handling the coupling while it is cryogenically cold. It is also an object of the present invention to provide insulation that is flexible at cryogenic temperatures to protect the operating person from the cryogenic cold. When the above objects are taken in total, it is an object of the present invention to provide a means for transfer of cryogenic fluids in such a way that the cryogenic nature of the fluid being transferred is essentially "invisible" to the operating person.